ATI

Sulfides can be found naturally in well water and can build up in wastewater collection systems due to anaerobic conditions frequently found there. In addition, sulfides are used in mercury removal processes and are frequently found in tanning wastes. In drinking water systems, sulfides cause taste and odor problems. In wastewater systems, sulfides cause damage to concrete structures in collection systems and contribute to odor problems in treatment facilities.

Measurement of dissolved sulfide concentrations has been done primarily by the use of analyzers employing ion-selective electrodes (ISE) for sensing. While providing adequate sensitivity, ISE-based systems require frequent zero and span adjustments to maintain measurement accuracy. Because of this, most ISE-based monitoring systems are relatively expensive and require frequent service.

Due to measuring sulfides in the solution being relatively difficult, the Q46S/81 Monitor takes a different approach to the measurement, employing a unique gas-phase method to continuously monitor sulfide without contact between the sensor and the water sample. In operation, a small amount of sample is pumped into the system and mixed with acid. In an acidic solution, the sulfide ion is converted to hydrogen sulfide gas The mixed sample flows into a special chamber where the hydrogen sulfide is stripped from the sample. A gas conditioning module prepares the gas sample for measurement prior to contacting with a special H₂S gas sensor designed for the system. Sensor signals are amplified and displayed on a large-format, backlit LCD display in the Q46S electronics unit.